Nutzung von Resistenzmechanismen verschiedener Rebarten als Alternative zum Einsatz von Kupfer im Ökoweinbau

Extrakte aus Wildreben bzw. Hybriden mit hoher Resistenz: Es war zu prüfen, ob durch die Applikation von Blattextrakten von Nicht-Vitis-vinifera-Rebsorten auf Qualitätsrebsorten Plasmopara viticola und andere Pathogene bekämpft, unterdrückt oder pflanzeneigene Abwehrmechanismen bei Qualitätsrebsorten durch in den Extrakten enthaltene Elicitoren aktiviert werden können resp. ob mit den Pflanzenextrakten eine direkte Bekämpfung dieser Problemschaderreger möglich ist. Kupferreduktionspotential bei Anbau neuer Vitis vinifera PIWI - Sorten: Der Anbau von PIWI’s ermöglicht einen weitgehenden Verzicht auf Pflanzenschutz und ist ökologisch und ökonomisch die nachhaltigste Form des Weinbaus überhaupt. Das Kupfereinsparungspotential durch den Anbau von PIWI’s ist vermutlich abhängig von der Resistenz der Sorte und von den klimatischen Bedingungen am Standort. Das für die jeweilige Sorte notwendige Maß an Pflanzenschutz soll in diesem Projekt erstmals ermittelt werden. Daraus lässt sich ein durchschnittliches Einsparpotential an Kupfer bestimmen. Orientierungsversuche mit geringen Stockzahlen im Freiland an Zuchtstämmen mit bereits pyramidisierten Plasmopara Resistenzen wurden in einer 2009 erstellten Prüfanlage mit Überkronenberegnung durchgeführt, in der beliebig hohe Befallsbedingungen für die Rebenperonospora geschaffen werden können

Damage segregation at fissioning may increase growth rates: A superprocess model

A fissioning organism may purge unrepairable damage by bequeathing it preferentially to one of its daughters. Using the mathematical formalism of superprocesses, we propose a flexible class of analytically tractable models that allow quite general effects of damage on death rates and splitting rates and similarly general damage segregation mechanisms. We show that, in a suitable regime, the effects of randomness in damage segregation at fissioning are indistinguishable from those of randomness in the mechanism of damage accumulation during the organism's lifetime. Moreover, the optimal population growth is achieved for a particular finite, non-zero level of combined randomness from these two sources. In particular, when damage accumulates deterministically, optimal population growth is achieved by a moderately unequal division of damage between the daughters. Too little or too much division is sub-optimal. Connections are drawn both to recent experimental results on inheritance of damage in protozoans, to theories of the evolution of aging, and to models of resource division between siblings.Comment: Version 2 had significant conceptual and organizational changes, though only minor changes to the mathematics. Version 3 has minor proofreading corrections, and a few new references. The paper will appear in Theoretical Population Biolog

Eco-evolutionary dynamics in fragmented landscapes

Peer reviewedPostprin

Moment Closure - A Brief Review

Moment closure methods appear in myriad scientific disciplines in the modelling of complex systems. The goal is to achieve a closed form of a large, usually even infinite, set of coupled differential (or difference) equations. Each equation describes the evolution of one "moment", a suitable coarse-grained quantity computable from the full state space. If the system is too large for analytical and/or numerical methods, then one aims to reduce it by finding a moment closure relation expressing "higher-order moments" in terms of "lower-order moments". In this brief review, we focus on highlighting how moment closure methods occur in different contexts. We also conjecture via a geometric explanation why it has been difficult to rigorously justify many moment closure approximations although they work very well in practice.Comment: short survey paper (max 20 pages) for a broad audience in mathematics, physics, chemistry and quantitative biolog

Is Bacterial Persistence a Social Trait?

The ability of bacteria to evolve resistance to antibiotics has been much reported in recent years. It is less well-known that within populations of bacteria there are cells which are resistant due to a non-inherited phenotypic switch to a slow-growing state. Although such ‘persister’ cells are receiving increasing attention, the evolutionary forces involved have been relatively ignored. Persistence has a direct benefit to cells because it allows survival during catastrophes–a form of bet-hedging. However, persistence can also provide an indirect benefit to other individuals, because the reduced growth rate can reduce competition for limiting resources. This raises the possibility that persistence is a social trait, which can be influenced by kin selection. We develop a theoretical model to investigate the social consequences of persistence. We predict that selection for persistence is increased when: (a) cells are related (e.g. a single, clonal lineage); and (b) resources are scarce. Our model allows us to predict how the level of persistence should vary with time, across populations, in response to intervention strategies and the level of competition. More generally, our results clarify the links between persistence and other bet-hedging or social behaviours

How Microbial Community Composition Regulates Coral Disease Development

Modeling reveals how rapid overgrowth by pathogenic microbes in the mucus layer surrounding corals, which often occurs under temporary stressful conditions, can persist long after environmental conditions return to normal

Mate choice for genetic quality when environments vary: suggestions for empirical progress

Mate choice for good-genes remains one of the most controversial evolutionary processes ever proposed. This is partly because strong directional choice should theoretically deplete the genetic variation that explains the evolution of this type of female mating preferences (the so-called lek paradox). Moreover, good-genes benefits are generally assumed to be too small to outweigh opposing direct selection on females. Here, we review recent progress in the study of mate choice for genetic quality, focussing particularly on the potential for genotype by environment interactions (GEIs) to rescue additive genetic variation for quality, and thereby resolve the lek paradox. We raise five questions that we think will stimulate empirical progress in this field, and suggest directions for research in each area: 1) How is condition-dependence affected by environmental variation? 2) How important are GEIs for maintaining additive genetic variance in condition? 3) How much do GEIs reduce the signalling value of male condition? 4) How does GEI affect the multivariate version of the lek paradox? 5) Have mating biases for high-condition males evolved because of indirect benefits

Invasion fitness, inclusive fitness, and reproductive numbers in heterogeneous populations.

How should fitness be measured to determine which phenotype or "strategy" is uninvadable when evolution occurs in a group-structured population subject to local demographic and environmental heterogeneity? Several fitness measures, such as basic reproductive number, lifetime dispersal success of a local lineage, or inclusive fitness have been proposed to address this question, but the relationships between them and their generality remains unclear. Here, we ascertain uninvadability (all mutant strategies always go extinct) in terms of the asymptotic per capita number of mutant copies produced by a mutant lineage arising as a single copy in a resident population ("invasion fitness"). We show that from invasion fitness uninvadability is equivalently characterized by at least three conceptually distinct fitness measures: (i) lineage fitness, giving the average individual fitness of a randomly sampled mutant lineage member; (ii) inclusive fitness, giving a reproductive value weighted average of the direct fitness costs and relatedness weighted indirect fitness benefits accruing to a randomly sampled mutant lineage member; and (iii) basic reproductive number (and variations thereof) giving lifetime success of a lineage in a single group, and which is an invasion fitness proxy. Our analysis connects approaches that have been deemed different, generalizes the exact version of inclusive fitness to class-structured populations, and provides a biological interpretation of natural selection on a mutant allele under arbitrary strength of selection

Infection Process and Mycotoxin Production in Fusarium Culmorum-infected Maize Ears

Red ear rot of maize is an important disease in Europe caused by toxigenic Fusarium species like F.  graminearum and F. culmorum. To get detailed information about the pathogenesis of the disease and the  Fusarium toxin production in infected ears a field study was conducted with maize which was artificially  inoculated with F. culmorum at the stage of female flowering. Every fortnight after inoculation, maize ears of  two varieties were harvested and analysed for the progress of visual signs of the disease and related Fusarium  toxin contamination. During the last harvest in mid October, external infection symptoms showing some small  pale or brown-marbled kernels with dark brown rachillae were only observed at the ear tip, whereas internal  symptoms visible within the rachis were much more pronounced and showed greyish –brownish or pink discolouration of the pith. The symptoms observed in rachis and kernels corresponded with the toxin contamination showing considerably higher concentrations in the rachis compared to the kernels and a top-down gradient from high to low toxin levels within the ear. This suggests that F. culmorum first infects the rachis from  the tip towards the bottom, as it subsequently does the kernels via the rachillae connected to the rachis. As  infection symptoms and mycotoxin production were much more pronounced in the rachis than in the kernels, red ear rot evaluation should be improved by observing signs of the disease in both kernels and the rachis